In an electric rotating machine utilizing permanent magnets, as magnets in the rotor, rare-earth magnets that have strong magnetic force and are typified by a neodymium-system sintered magnet are utilized for the purpose of downsizing, output-boosting, and efficiency-raising of the electric rotation machine. Patent Document 1 discloses an example of electric rotating machine in which in order to increase the quantity of magnetic flux in the stator, the magnets in the rotor are arranged in a Halbach array. In the example disclosed in Patent Document 1, the magnetic poles in the rotor are configured with main magnets and auxiliary magnets; the main magnets whose magnetization direction is the radial direction and the auxiliary magnets whose magnetization direction is the circumferential direction are alternately arranged; in order to increase the quantity of magnetic flux, the relationship between the circumferential-direction width Ws of the stator-side face of an auxiliary magnet and the radial-direction thickness t of said auxiliary magnet is set in such a way that 0<Ws<1.5 t.
Patent Document 2 also discloses an electric rotating machine having a Halbach-array rotor; Patent Document 2 discloses an example in which the radial dimension of the auxiliary magnet is made shorter than that of the main magnet so that finish work is omitted and hence ease of assembly is enhanced.